[Bug rtl-optimization/58679] [4.9 regression] ICE in create_pre_exit, at mode-switching.c:421 with -mavx after r202915

[ubizjak at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58679

--- Comment #5 from Uroš Bizjak <ubizjak at gmail dot com> ---
Another problem:

--cut here--
int f (long long a, long long b)
{
  return (a * b) >> 16;
}
--cut here--

-O2 -mavx -m32 results in the ICE in mode switching due to following sequence:

(insn 14 12 23 2 (parallel [
            (set (reg:DI 0 ax [orig:99 D.1985 ] [99])
                (ashiftrt:DI (reg:DI 0 ax [orig:97 D.1985 ] [97])
                    (const_int 16 [0x10])))
            (clobber (reg:CC 17 flags))
        ]) t-2.c:3 528 {*ashrdi3_doubleword}
     (nil))
(insn 23 14 30 2 (use (reg/i:SI 0 ax)) t-2.c:4 -1
     (nil))

The set and use have different modes. Before the change:

(insn 14 12 20 2 (parallel [
            (set (reg:DI 0 ax [orig:99 D.1985 ] [99])
                (ashiftrt:DI (reg:DI 0 ax [orig:97 D.1985 ] [97])
                    (const_int 16 [0x10])))
            (clobber (reg:CC 17 flags))
        ]) t-2.c:3 528 {*ashrdi3_doubleword}
     (nil))
(insn 20 14 23 2 (set (reg/i:SI 0 ax)
        (reg:SI 0 ax [orig:99 D.1985 ] [99])) t-2.c:4 86 {*movsi_internal}
     (nil))
(insn 23 20 30 2 (use (reg/i:SI 0 ax)) t-2.c:4 -1
     (nil))